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These visuals are methods of managing pixel color on the display. There are seven
types of visuals available, as shown in Table 9-1; the number after each visual class
9.2
9.2 Visuals 137
name is the visual class number used by the X protocol. The output from xdpyinfo
shows the visual class along with information about the size of the colormaps, the
order of the RGB color information within the pixel color (controlled by the mask),
and the size of each color component (significant bits).
A colormap (or palette) is a numbered list of colors; a good analogy is that of a paintby-
number kit, where the number given for each area in the image is looked up in the
colormap to determine the color to paint. In a similar way, the StaticColor and
PseudoColor visuals interpret each pixel??™s value in the video framebuffer as a color
number which is looked up in the colormap; the color specified by the red, green,
and blue values in the colormap is drawn on the screen. A StaticColor visual uses
preset colors (such as the 16 VGA colors) while a PseudoColor visual allows the colors
to be adjusted.
Changing a PseudoColor colormap entry will cause all pixels that are displayed in that
color to immediately change.
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